The present invention relates generally to safety hitches for coupling conventional highway trailers to tractors or to one another in tandem. More specifically, the present invention is directed to an improved safety trailer hitch which facilitates automatic coupling of trailer and tractor by the driver without manual intervention and the resultant risk of human injury. The invention is believed best classified in U.S. utility class 213, subclass 86.
Trucking has become a major industry in the United States. As the industry has grown and developed, a great number of devices have been introduced for enhancing both the safety and the simplicity of tractor-trailer operation. It will be appreciated that the use of inadequate and unsure trailer hitches in the past has resulted in numerous serious and fatal accidents on our highways. In recent years, more complex hitching systems have been developed to overcome previous safety hazards, but their use typically requires increased manual intervention in the tractor-trailer coupling process. Consequently, labor costs and the frequency of personal injuries resulting from manual coupling operations increase. Hence, advances in safety have proved very costly to truckyard operators.
In the experience of those familiar with prior art pintle hitch systems for tractor-trailer coupling, it is usually necessary for the driver to carefully maneuver the tractor into straight alignment with the trailer hitch to effectuate a proper coupling The truck driver must back the tractor generally in the direction of the stationary trailer. It is thus very difficult to achieve satisfactory alignment of the hitch and the trailer. Proper alignment is even more difficult to obtain where two or more trailers are to be hooked in tandem. Because exact alignment is rarely accomplished in this manner, manual intervention in the hitching process is nearly always necessary. For example, time and motion analyses conducted with typical pintle-hook hitching systems indicated that a driver will need to dismount from the tractor on the average of eleven times in the process of coupling and uncoupling two trailers. Typical coupling time is estimated at roughly one hour, where numerous such attempts to achieve proper alignment are necessary. Uncoupling time typically runs thirty to fifty minutes with these systems.
It would thus seem desirable to provide a hitching system which would readily guide the driver to attain proper alignment of the trailer drawbar with the hitch as he maneuvers the vehicle. It is particularly desirable to provide a hitching system which can be safely connected entirely without or at least with minimal manual intervention by the driver or other truckyard workers.
To achieve drawbar-hitch alignment, commercial trucking operations typically use a trailer dolly associated with a tow vehicle known as a "yard-dog" which can move a trailer around the truckyard or loading area into relatively close alignment for connection to a desired tractor hitch. However, even with the aid of such tow devices, precise hitching alignment is difficult to achieve. Moreover, once the tow device is removed, the loaded dolly cannot be moved by a truckyard worker to perfect alignment.
As a result, truckyard workers will typically apply whatever tool or device is available to them to force the trailer tongue into the hitch. Hammering the hitch or pounding the tongue into position often results in permanent structural damage to the hitch which may affect the quality and safety of the connection. Moreover, such techniques greatly increase the likelihood of injury to the worker's hands and arms. Additionally, if the drawbar of a pintle-hook hitch system should drop during installation, for example, the operator's legs or feet may be seriously injured.
In the prior art, a wide variety of hitching devices have been developed to facilitate coupling of utility trailers to highway tractors for long distance hauling. Representative of prior art safety hitch technology presently in use are the hook hitches illustrated in U.S. Pat. No. 4,279,431, issued on July 21, 1981 to Schott; and, in U.S. Pat. No. 4,492,386, issued to Roberts on Jan. 8, 1985. Such hitches typically comprise a rigid tongue-receptive jaw operatively associated with a lock mechanism which may be locked upon or about a trailer tongue.
For example, the Schott '431 trailer hook includes a spring-biased release latch which must be manually actuated by pressure applied by a truckyard worker. As will be appreciated, the release of the tensioned lock mechanism commonly results in injuries to the worker's hand either when the locking mechanism is pushed out of the interior of the trailer hook housing or when the latch rebounds back into its resting position.
The Roberts '386 device is a pintle hook hitch which includes a manually actuable pivotal locking mechanism. The locking mechanism comprises a retainer arm adapted to close the jaw of the trailer hook upon the hitch associated with a pivoting latch body. To prevent the worker's hands from contacting or interfering with the spring-biased retainer arm, the Roberts device includes an actuator latch positioned upon the lower portion of the hitch and spaced apart from the retainer arm. The free-swinging pivoting latch is adapted to automatically swing into locking position under the force of gravity when the worker releases the actuator latch.
Tractor-trailer hitches which embody the principles set forth in the aforementioned patents and which are presently available on the market include the Premier Model 270 Rear Hitch (Part No. 15-0-29); Holland Model T-60-AL Rear Hitch (Part No. 15-0-35); and, the Trailmobile Rear Hitch (Part No. 15-0-25).
One major disadvantage of such prior art locking hitch systems is that they require manual actuation by the driver or truckyard worker. There is also substantial risk with the use of such devices that the driver or worker will, through inadvertence, inattentiveness, or mere haste fail to secure the locking mechanism into position before driving the vehicle. Such failure is particularly likely where improper hitch alignment requires the worker to force the connection and makes locking extremely difficult or impossible. Without proper safety locking mechanisms deployed, even the most complex prior art hitches are unsafe. Hence it would seem desirable to provide an automatic coupling safety hitch assembly which automatically engages the safety locking mechanism when it is connected. None of the prior art hitches known to us employ such a safety feature.
Various types of automatic locking couplings have been known and used previously in the railroad industry. Typical of such couplings is U.S. Pat. No. 4,311,244, issued to Hindin et al. on Jan. 19, 1982. However, such technology finds little application in the trucking industry, since it is typically extremely complex and is not practical for adaptation to conventional tractor-trailer hitching systems. None of the prior art known to me has successfully incorporated or adapted the broad concepts applied in railroad coupling technology to tractor-trailer hitching systems. Hence it is desired to provide a tractor-trailer hitching system which incorporates some of the most advantageous safety features commonly used and known in the railroad industry.